[otreblatercero]

I think it's not so good advice. I have read many books which took me many, many attempts to get to the point of no return to love them and finish them, most of those books are now my favorites. The consumerist approach of giving 50 pages would be better suited for red flags, for example, if it's a theme you don't like, or maybe, just maybe, something against your personal beliefs and values. Life is too short to not give a chance to literature masterpieces.

[RheingoldRiver]

I think good advice is something along the lines of: "Find a good book discussion group" (for me this is /r/Fantasy). "Then, if you aren't liking a book somewhat significantly into it, explain to people there why you don't like it and should you keep reading it."

This method is pretty effective in a good discussion group because if you have explained your reasons well, people will understand your reasons for dislike and know whether things change; the payoff is worth it; the author improves; etc.

One example is The Licanius Trilogy. A lot of people say, "I read book 1, I hate it, should I finish it" and depending on how much they hated book 1 and their reading speed people will give differing advice. For example if you can finish the trilogy in 5 days (this is about how fast I read it) I would say yes, the ending is fantastic but the books are pretty dreadful in terms of prose quality and character depth. However if this will take you 6 months, no, bail out now and spend your time better. Read a plot summary on Wikipedia.

Reading is very much a social activity and much better when treated as such imo.

[karaterobot]

Whatever heuristic you want to use is fine, the key thing is that if it fails your test, you have to be willing to put it down and move on to the next book. Don't get caught up on 50 pages, it's an arbitrary number.